A photonic integrated circuit (PIC) having a substrate in which vertically coupled photodetectors and in-line optical modulators are integrated to enable vertical coupling of light using a fiber assembly block (FAB), with the planar end surface thereof being attached to a substantially planar main surface of the substrate. In an example embodiment, the photodetectors are buried in deep vias formed in the substrate, and the in-line optical modulators are waveguide-connected to the corresponding vertical-coupling optical gratings. The photodetectors and optical gratings may be arranged in a linear array along the main surface of the substrate to enable uncomplicated optical alignment of end segments of the optical fibers in the FAB with the corresponding photodetectors and optical gratings for vertical coupling of light therebetween. In some embodiments, the FAB may have more than one hundred optical fibers. In some embodiments, the PIC can be implemented using the silicon photonics material platform.
|
1. An apparatus comprising:
a substrate having a substantially planar main surface;
a plurality of photodiodes integrated in the substrate to enable vertical coupling of input light into the photodiodes such that one of the photodiodes receives part of the input light through an area of said main surface vertically above said one of the photodiodes; and
a plurality of in-line optical modulators integrated in the substrate and waveguide-connected in the substrate to a plurality of first vertical-coupling elements to enable vertical coupling of output light therefrom through said main surface.
2. The apparatus of
3. The apparatus of
4. The apparatus of
5. The apparatus of
6. The apparatus of
7. The apparatus of
8. The apparatus of
9. The apparatus of
10. The apparatus of
11. The apparatus of
12. The apparatus of
13. The apparatus of
14. The apparatus of
wherein each of the optical data receivers comprises a respective one of the photodiodes.
15. The apparatus of
16. The apparatus of
wherein the substrate comprises a base layer, an insulator layer, and a device layer arranged in a vertical stack; and
wherein the vias penetrate the device layer and enter the insulator layer.
17. The apparatus of
the base layer comprises silicon;
the insulator layer comprises silicon oxide;
the device layer comprises silicon; and
the photodiodes comprise germanium.
18. The apparatus of
|
Various example embodiments relate to optical communication equipment and, more specifically but not exclusively, to optical transmitters and receivers.
This section introduces aspects that may help facilitate a better understanding of the disclosure. Accordingly, the statements of this section are to be read in this light and are not to be understood as admissions about what is in the prior art or what is not in the prior art.
The demand for higher data rates and lower latency drives the application of new technologies in communications. For example, optical communication technologies can be used to support the current and future data-rate and latency needs. The corresponding circuits may employ electrical and/or optical components configured to exchange relatively large volumes of data at a relatively high rate. However, solutions that are based on scaling up conventional electrical-to-optical (E/O) and/or optical-to-electrical (O/E) front-end circuits may encounter significant problems, such as challenging thermal-management issues, packaging constrains, manufacturability, reliability, and/or tougher power-efficiency restrictions.
Disclosed herein are various embodiments of a photonic integrated circuit (PIC) having a substrate in which vertically coupled photodetectors and in-line optical modulators are integrated to enable vertical coupling of light using a fiber assembly block (FAB), with a planar end surface thereof being attached to a substantially planar main surface of the substrate. In an example embodiment, the photodetectors are buried in deep vias formed in the substrate, and the in-line optical modulators are waveguide-connected in the substrate to the corresponding vertical-coupling optical gratings. The photodetectors and optical gratings may be arranged in a linear array along the main surface of the substrate to enable uncomplicated optical alignment of end segments of the optical fibers in the FAB with the corresponding photodetectors and optical gratings for vertical coupling of light therebetween. In some embodiments, the FAB may have more than one hundred optical fibers. In some embodiments, the PIC can be implemented using the silicon photonics material platform.
According to an example embodiment, provided is an apparatus comprising: a substrate having a substantially planar main surface; a plurality of photodiodes integrated in the substrate to enable vertical coupling of input light thereto through said main surface; and a plurality of in-line optical modulators integrated in the substrate and waveguide-connected in the substrate to a plurality of first vertical-coupling elements to enable vertical coupling of output light therefrom through said main surface.
Other aspects, features, and benefits of various disclosed embodiments will become more fully apparent, by way of example, from the following detailed description and the accompanying drawings, in which:
Some embodiments may benefit from the use of at least some features described in U.S. patent application Ser. No. 16/855,618, which is incorporated herein by reference in its entirety.
Some embodiments may benefit from the use of at least some features described in U.S. patent application Ser. No. 16/595,698, which is incorporated herein by reference in its entirety.
In some embodiments, optical transmitters 1741-174N may receive respective optical carriers, for modulation therein, from one or more external light sources (e.g., lasers; not explicitly shown in
In some embodiments, the number N of optical transmitters 174 may be different from the number M of optical receivers 184. In some other embodiments, N=M.
In some embodiments, the number N can be N=1.
In some embodiments, the number M can be M=1.
System 100 further comprises a core electrical circuit (e.g., an ASIC) 102 that is electrically linked to optical transmitters 174 and optical receivers 184 as explained in more detail below. As a result, circuit 102 can transmit data signals by way of optical transmitters 174 and can receive data signals by way of optical receivers 184.
The function of the core electrical circuit 102 may depend on the specific embodiment. For example, in some embodiments, system 100 can be an NxM optical-electrical-optical (OEO) switch configured to perform signal switching in the electrical domain using a corresponding N×M electrical switch implemented by the core electrical circuit 102.
In some other example embodiments, system 100 can be a multichannel OEO 3R converter. Herein, 3R stands for re-timing, re-shaping, and re-amplifying data signals. This type of system 100 can be used, e.g., for changing the assignment of carrier wavelengths of some data signals transmitted therethrough. In such embodiments, the core electrical circuit 102 is designed to support the indicated conversion.
In other example embodiments, the system architecture indicated in
In an example embodiment, system 100 comprises N transmit-channel circuits 1041-104N associated with the optical transmitters (OTx's) 1741-174Nrespectively, and M receive-channel circuits 1061-106M associated with the optical receivers (ORx's) 1841-184M, respectively. In some embodiments, the N transmit channels may be implemented using N nominally identical circuits, e.g., different respective instances (nominal copies) of the same transmit-channel circuit. Similarly, the M receive channels may be implemented using M nominally identical circuits, e.g., different respective instances of the same receive-channel circuit.
In an example embodiment, a transmit-channel circuit 104n (where n=1, . . . , N) comprises a first interface circuit 118n, a second interface circuit 132n, and a serializer 136n that are serially connected in the transmit chain between the core electrical circuit 102 and optical transmitter 174n using electrical buses 112n, 120n, 134n, and 138n. Each of electrical buses 112n, 120n, and 134n is a q-bit bus, e.g., implemented using q parallel electrical lines, where q is an integer greater than one. Electrical bus 138n is an r-bit bus, where r is an integer constrained by the inequality 1<r<q.
In an example embodiment, the following values of q and r may be used: q=128; r=2.
In some embodiments, r=1. In such embodiments, electrical bus 138n is replaced by a corresponding single electrical line.
In some embodiments, electrical bus 120n may have a different number of parallel electrical lines than electrical buses 112n, 116n, and 134n. For example, the number of parallel electrical lines in electrical bus 120n may be greater or smaller than the number q.
In an example embodiment, optical transmitter 174n may be configured to generate the corresponding optical output signal using an optical PAM-2r constellation such that, in each modulation time slot, the transmitted PAM-2r optical symbol carries the corresponding r bits applied to the optical transmitter by electrical bus 138n. Herein, PAM stands for pulse-amplitude modulation. A person of ordinary skill in the art will understand that other suitable optical constellations may alternatively be selected based on the number r.
In some embodiments, the total data rate at which electrical bus 112n transmits data may be higher than, e.g., 1000 Mbps. In various embodiments, any suitable electrical modulation format can be used. Examples of such formats include but are not limited to binary non-return-to-zero (NRZ), binary return-to-zero (RZ), PAM, etc.
Electrical bus 120n is typically of a greater physical length than the other electrical buses of transmit-channel circuit 104n. Interface circuits 118n and 132n may perform signal transformation and/or coding/decoding directed at making the electrical signals transmitted on electrical bus 120n more resilient to the relatively strong signal distortions and loss that are typically caused by the transmission through a relatively long parallel electrical bus.
For example, each of the electrical data signals transmitted on electrical bus 112n may be a sequence of binary NRZ waveforms in which one constant voltage level represents a binary “1” and the other constant voltage level represents a binary “0.” In such an electrical data signal, a repeating “01” bit sequence may be represented by a sequence of substantially rectangular pulses, the rising and falling edges of which cause said electrical data signal to have relatively strongly pronounced high-frequency components that would be susceptible to strong distortions and loss in electrical bus 120n. However, interface circuit 118n may be configured to transform a sequence of binary NRZ waveforms into a sequence of other waveforms that are shaped such as to significantly reduce the rate(s) of distortions and loss to which the resulting electrical signal is subjected in electrical bus 120n. Interface circuit 132n can then be used to substantially recover the initial binary NRZ waveforms based on said other waveforms received via electrical bus 120n from interface circuit 118n. The recovered binary NRZ waveforms are then transmitted further downstream on electrical bus 134n. Herein, NRZ stands for non-return-to-zero.
The number of parallel electrical lines and per-line bit rate for electrical bus 120n may be selected such as to keep the amounts of signal processing in interface circuits 118n and 132n relatively small but sufficient for preserving the integrity of the electrical data signals transmitted through this electrical bus.
In an example embodiment, serializer 136n operates to compress the q bit streams applied thereto by electrical bus 134n into r bit streams, which are then transmitted downstream by way of electrical bus 138n. Due to this compression, the resulting electrical data signals transmitted on electrical bus 138n are switched at a higher frequency rate than the corresponding electrical data signals transmitted on electrical bus 134n. As already indicated above, in some embodiments, the number r may be r=1. In such embodiments, serializer 136n operates to compress the q received bit streams into a corresponding single bit stream.
In an example embodiment, a receive-channel circuit 106m (where m=1, . . . , M) comprises a deserializer (DES) 156m, a first interface circuit 152m, and a second interface circuit 128m that are serially connected in an electrical receive chain between the optical receiver 184m and core electrical circuit 102 using electrical buses 122m, 140m, 154m, and 158m. Each of electrical buses 122m, 140m, and 154m is a t-bit bus, where t is an integer greater than one. Electrical bus 158m is a u-bit bus, where u is an integer constrained by the inequality 1<u<t.
In an example embodiment, the following values oft and u may be used: t=128; u=2.
In some embodiments, u=1. In such embodiments, electrical bus 158m is replaced by a corresponding single electrical line.
In some embodiments, electrical bus 140m may have a different number of parallel electrical lines than either of electrical buses 122m and 154m. For example, the number of parallel electrical lines in electrical bus 140m may be greater or smaller than the number t.
In an example embodiment, optical receiver 184m may be configured to detect a received optical input signal that has been generated by the corresponding remote optical transmitter using a PAM-2u constellation such that, in each modulation time slot, the transmitted PAM-2u optical symbol carries the corresponding u bits. A person of ordinary skill in the art will understand that the use of other optical constellations is also possible, with the constellation selection being made, e.g., based on the number u.
In an example embodiment, deserializer 156m operates to decompress the u bit streams applied thereto by electrical bus (or single line) 158m into t bit streams, which are then transmitted upstream by way of electrical bus 154m. Due to this decompression, the resulting electrical data signals transmitted on electrical bus 154m are switched at a lower frequency rate than the corresponding electrical data signals transmitted on electrical bus (or single line) 158m.
The physical length of electrical bus 140m may be similar to that of electrical bus 120n. The physical length of electrical bus 140m is also typically greater than the physical lengths of the other electrical buses of receive-channel circuit 106m (also see
In various embodiments, any suitable electrical modulation format can be used for data transmission on electrical bus 122m. Examples of such formats include but are not limited to NRZ, RZ, and PAM.
The dashed lines in
A first integrated circuit, labeled 110, may be an ASIC that includes the core electrical circuit 102, interface circuits 1181-118N and 1281-128M, and electrical buses 1121-112N and 1221-122M.
A second integrated circuit, labeled 130, may be configured to drive the optical modulators of optical transmitters 1741-174N in response to the data signals received via electrical buses 1201-120N from circuit 110. Circuit 130 may further be configured to perform signal processing to recover the data encoded in the received optical signals by demodulating the corresponding electrical signals generated by the light detectors of optical receivers 1841-184M. For example, circuit 130 may include interface circuits 1321-132N, serializers 1361-136N, drive-circuit portions of optical transmitters 1741-174N, electrical buses 1341-134N and 1381-138N, amplifier portions and signal slicers of optical receivers 1841-184M, deserializers 1561-156M, interface circuits 1521-152M, and electrical buses 1541-154M and 1581-158M.
A third integrated circuit, labeled 170, may be an electro-optical circuit that includes the optical modulators of optical transmitters 1741-174N, light detectors of optical receivers 1841-184M (also see
In various alternative embodiments, other packaging solutions can be used to implement system 100. For example, packaging solutions that involve two, four, five, or eleven IC chips are contemplated. In general, system 100 can be implemented using any suitable, practically feasible number of IC chips.
In some embodiments, buses 138n and 158m may be relatively long to enable better thermal isolation between at least some parts of IC chip 170 and some heat generating digital electronics in IC chip 130.
In some embodiments, the SERDES 136/156 in system 100 can be replaced by a multi-stage SERDES similar to the SERDES disclosed in the above-cited U.S. patent application Ser. No. 16/595,698. In such embodiments, a first stage of the SERDES may be located in IC chip 110, e.g., near the core electrical circuit 102, and a second stage of the SERDES may be located in IC chip 130.
In some embodiments, system 100 may have a single-stage SERDES located in IC chip 110, e.g., near the core electrical circuit 102.
In some embodiments, placement of a single-stage SERDES or a multi-stage SERDES in system 100 may be specifically engineered to enable better heat management in system 100.
In an example embodiment, optical transmitter 174n comprises a constellation mapper 210, a driver circuit 220, a laser 230, and an optical modulator 240. In operation, constellation mapper 210 uses the operative constellation (e.g., a PAM-2r constellation) and a bit word supplied by electrical bus 138n to determine a constellation symbol for a corresponding modulation time slot. A resulting stream 212 of such constellation symbols is applied to the driver circuit 220 that converts said stream, as known in the pertinent art, into one or more drive voltages and/or currents 222 for the optical modulator 240. In response to said one or more drive voltages and/or currents 222, the optical modulator 240 modulates an optical carrier 232 generated by the laser 230. A resulting modulated optical signal 242 is then directed to optical output port 178n for further transmission.
In different embodiments, optical modulator 240 can be implemented, e.g., using one or more of the following optical modulators: (i) a Mach-Zehnder modulator; (ii) a ring modulator; and/or (iii) an electro-absorption modulator.
In the shown embodiment, laser 230 is located off-chip and is optically connected to an optical input port 288 of integrated circuit 170 using an optical fiber 286. In an alternative embodiment, laser 230 may be a part of integrated circuit 170. In such an embodiment, on-chip optical waveguides may be used instead of optical fiber 286 to optically connect laser 230 and optical modulator 240.
In an example embodiment, optical receiver 184m comprises a photodetector (e.g., a photodiode) 310, an amplifier 320, and a signal slicer 330. In response to a received modulated optical signal 308, photodetector 310 generates a corresponding electrical signal 312. Amplifier 320 operates to amplify electrical signal 312, thereby generating an amplified electrical signal 322. In each modulation time slot, slicer 330 compares samples of electrical signal 322 with a set of threshold voltages and, based on the comparison, determines the corresponding bit words for the electrical bus 158m. The determined bit words, each of which has u bits, are outputted bitwise on the parallel lines of electrical bus 158m.
In an example embodiment, amplifier 320 can be a multi-stage amplifier that includes a transimpedance amplifier (TIA) and one or more variable-gain amplifiers (VGAs) as stages thereof. A closed loop can be used to implement automatic gain control for amplifier 320, e.g., as known in the pertinent art. Peaking control can be used to appropriately shape the frequency response of amplifier 320, e.g., as known in the pertinent art. Slicer 330 is clocked using a clock signal CLK. The threshold voltages used in slicer 330 are set using a control signal 328.
As used herein, the term “photonic integrated circuit” (or PIC) should be construed to cover planar lightwave circuits (PLCs), integrated optoelectronic devices, wafer-scale products on substrates, individual photonic chips and dies, and hybrid devices. Example material systems that can be used for manufacturing various PICs may include but are not limited to III-V semiconductor materials, silicon photonics, silica-on-silicon products, silica-glass-based PLCs, polymer integration platforms, Lithium Niobate and derivatives, nonlinear optical materials, etc. Both packaged devices (e.g., wired-up and/or encapsulated chips) and unpackaged devices (e.g., dies) can be referred to as PICs.
PICs can be used for various applications in telecommunications, instrumentation, and signal-processing fields. A PIC typically uses optical waveguides to implement and/or interconnect various circuit components, such as optical switches, couplers, routers, splitters, multiplexers/demultiplexers, filters, modulators, phase shifters, lasers, amplifiers, wavelength converters, optical-to-electrical (O/E) and electrical-to-optical (E/O) signal converters, etc. A waveguide in a PIC is usually an on-chip solid light conductor that guides light due to an index-of-refraction contrast between the waveguide's core and cladding. A PIC typically comprises a planar substrate on which optoelectronic devices are grown by an additive manufacturing process and/or into which optoelectronic devices are embedded by a subtractive manufacturing processes, e.g., using a multi-step sequence of photolithographic and chemical processing steps.
An “optoelectronic device” interconverts between data-carrying electrical signals and data-carrying light and may include one or more of: (i) an electrically driven light source, such as a laser diode; (ii) an optical amplifier; (iii) an optical-to-electrical converter, such as a photodiode; and (iv) an optoelectronic component that can change one or more propagation properties, e.g., amplitude and/or phase of light, such as an optical modulator or a switch. The corresponding optoelectronic circuit may additionally include one or more optical elements and/or one or more electronic components that enable the use of the circuit's optoelectronic devices in a manner consistent with the circuit's intended function. Some optoelectronic devices may be implemented using one or more PICs.
As used herein, the term “integrated circuit” (IC) should be construed to encompass both a non-packaged die and a packaged die. In a typical IC-fabrication process, dies (chips) are produced in relatively large batches using wafers of silicon or other suitable material(s). Electrical and optical circuits can be gradually created on a wafer using a multi-step sequence of photolithographic and chemical processing steps. Each wafer is then cut (“diced”) into many pieces (chips, dies), each containing a respective copy of the circuit that is being fabricated. Each individual die can be appropriately packaged prior to being incorporated into a larger circuit or be left non-packaged.
The term “hybrid circuit” may refer to a multi-component circuit constructed of multiple monolithic ICs and possibly some discrete circuit components, all attached to each other to be mountable on and electrically connectable to a common base or carrier. A representative hybrid circuit may include (i) one or more packaged or non-packaged dies, with some or all of the dies including optical, optoelectronic, and/or semiconductor devices, and (ii) one or more optional discrete components, such as connectors, resistors, capacitors, and inductors. Electrical connections between the ICs, dies, and discrete components can be formed, e.g., using patterned conducting (such as metal) layers, ball-grid arrays, solder bumps, wire bonds, etc. The individual ICs may include any combination of one or more respective substrates, one or more redistribution layers (RDLs), one or more interposers, one or more laminate plates, etc.
In some embodiments, individual chips can be stacked. As used herein, the term “stack” refers to an orderly arrangement of packaged or non-packaged dies in which the facing and nearby main planes of the stacked dies are substantially parallel to each other. A stack can typically be mounted on a carrier in an orientation in which the main plains of the stacked dies are parallel to each other and/or to the main plane of the carrier.
A “main plane” of an object, such as a die, a PIC, a substrate, or an electronic IC, is a plane parallel to a substantially planar surface thereof that has the largest sizes, e.g., length and width, among all exterior surfaces of the object. This substantially planar surface may be referred to as a main surface. The feature height variation along the main surface may typically be much smaller than length or width, or both length and width, of said surface. In such cases, such main surface may be referred to as a substantially planar surface. The exterior surfaces of the object that have one relatively large size, e.g., length, and one relatively small size, e.g., height, are typically referred to as the edges of the object.
In the embodiment of
In operation, vertical-coupling elements 4100-4108 couple light to/from the on-chip optical waveguides of PIC 170. Herein, the “vertical” direction is parallel to the Z-coordinate axis and is a direction that is substantially (e.g., to within ±5 degrees) perpendicular to main surface 402. In the context of this disclosure, the term “vertical-coupling” denotes optical coupling at an angle that is out-of-plane relative to main surface 402, but not necessarily orthogonal to said main surface. For example, vertical coupling may be implemented at angles between 0 degrees and 45 degrees as measured with respect to the Z-coordinate axis. Vertical coupling may be performed from the top side (e.g., through main surface 402) of PIC 170 or from the opposing bottom side (e.g., the substrate side) of PIC 170.
In various embodiments, vertical-coupling elements 410 may be implemented using, e.g., turning mirrors, vertical grating couplers, elephant couplers, or three-dimensional (3D) optical coupling structures that may be 3D-printed onto PIC 170. Some embodiments may benefit from the use of one or more of the vertical-coupling elements disclosed in U.S. Pat. Nos. 8,750,654, 9,927,575, and 10,025,043 and U.S. Patent Application Publication Nos. 2015/0037044, 2015/0125110, 2015/0293305, 2018/0329159, and 2019/0258175, all of which are incorporated herein by reference in their entirety.
In an example embodiment, vertical-coupling element 4100 is a part of optical input port 288, which is fiber-connected to external laser 230 (e.g., as indicated in
In the shown embodiment, vertical-coupling element 4100 comprises an optical grating 510 and a tapered optical waveguide 520 connected to an on-chip optical waveguide 412 (also see
Referring back to
A ribbon optical modulator 240n comprises a sequence of serially connected optical modulators 440. In the shown embodiment, optical modulator 240n has a series of four optical modulators 440. In alternative embodiments, optical modulator 240n may have fewer or more than four optical modulators 440. For example, in some embodiments, each of ribbon optical modulators 2401-2408 may have, e.g., a series of twenty respective optical modulators 440. In some embodiments, an optical modulator 440 can be a traveling-wave Mach-Zehnder modulator. In some other embodiments, other suitable types of optical modulators may also be used to implement optical modulators 440.
In operation, different optical modulators 440 of a particular ribbon optical modulator 240n may be driven using the same data signal. The corresponding drive signals can be appropriately relatively delayed to coherently add the modulated signal portions to achieve a desired modulation depth at the output of the last optical modulator 440 of the sequence. Example drive circuits that can be used for driving optical modulators 440 in this manner are disclosed, e.g., in U.S. Patent Application Publication No. 2007/0237444, which is incorporated herein by reference in its entirety.
Optical modulators 440 and 240n may be referred to as in-line optical modulators. As used herein, the term “in-line optical modulator” refers to an optical modulator constructed to modulate light as the light propagates through an on-chip optical waveguide substantially parallel to a main surface of the corresponding PIC. An in-line optical modulator should be contrasted with a vertically coupled optical modulator, which is constructed to modulate light as the light propagates through the modulator substantially orthogonally to a main surface of the corresponding PIC.
In the shown embodiment, optical modulator 440 is a traveling-wave Mach-Zehnder modulator that comprises a 3-dB optical splitter 610 and modulator arms 6201 and 6202. At the output end of the modulator, modulator arms 6201 and 6202 are connected to an optical combiner (not explicitly shown in
In the shown embodiment, photodetector 310m comprises a photodiode 710 electrically connected to quasi-circular electrodes 720 and 730. A photosensitive area of photodiode 710 is located vertically beneath the inner opening of the O-shaped electrode 720 and is configured to receive input light vertically, i.e., along or at a small angle with respect to the Z-coordinate axis. In an example embodiment, electrode 720 may be electrically connected to the n portion of photodiode 710, and electrode 730 may be electrically connected to the p portion of photodiode 710. Electrical leads 722, 732, and 734 electrically connect electrodes 720 and 730 to contact pads 7401, 7402, and 7403, respectively, which may be used to appropriately electrically bias photodiode 710 and measure the photocurrent generated therein in response to the vertically received input light.
Referring back to
The embodiment illustrated in
In the embodiment shown in
In an example embodiment, silicon device layer 806 is patterned and etched in a conventional manner to create optical gratings 510 for vertical-coupling elements 4100-4108 and also at least some of the on-chip optical waveguides (e.g., 412, 520, and 620) of PIC 170. As a result, the top surfaces of these elements of PIC 170 are located at approximately the same vertical distance d from main surface 402 (see, e.g., elements 510 and 6202 in
In the example embodiment shown in
In operation, the p-n junction of optical waveguide 6202 functions as a phase shifter. For example, when a reverse bias is applied to the p-n junction, a depletion region forms within the waveguide. During the positive swing of the drive voltage applied between electrodes 6300 and 6302, the size of this depletion region increases, thereby decreasing the effective refractive index of the waveguide. During the negative swing of the drive voltage, the size of this depletion region decreases, thereby increasing the effective refractive index of the waveguide. This modulation of the effective refractive index causes the corresponding modulation of the phase of the light transmitted through waveguide 620.
In the example embodiment shown in
Photodiode 710 comprises semiconductor layers 822, 824, and 826 arranged in a vertical stack. Layer 822 is a relatively thin layer comprising p+-doped silicon. Layer 824 is a relatively thick layer comprising intrinsic germanium. Layer 826 is a relatively thin layer comprising n+-doped germanium. Layers 822, 824, and 826 thus form a p-Si/i-Ge/n-Ge heterojunction that can be electrically biased and operated using electrodes 720 and 730. More specifically, layer 822 is electrically connected to electrode 730, and layer 826 is electrically connected to electrode 720 as indicated in
As used herein, the term “reverse bias” refers to an electrical configuration of a semiconductor-junction diode in which the n-type material is at a high electrical potential, and the p-type material is at a low electrical potential. The reverse bias creates a relatively large electric field across the p-i-n junction that can efficiently separate the holes and electrons generated therein by the absorbed light. The separated electrical carriers generate a photocurrent that can be collected and measured as known in the art to determine the light intensity.
In an example embodiment, the layer stack 822/824/826 of photodiode 710 may be buried in a deep via 820 formed (e.g., etched) in SOI substrate layers 804 and 806. In some embodiments, the via 820 may also partially enter into the silicon base layer 802, e.g., as shown in
In some embodiments, the top surface of the layer stack 822/824/826 of photodiode 710 may be located at vertical distance d1 from the main surface 402 of PIC 170, while the top surfaces of the cores of waveguides 620 and of grating 510 are located at vertical distance d2 from the main surface 402 of PIC 170, where d1≠2. For example, the absolute value of the difference between the distances d1 and d2 may be smaller than approximately 100 nm, e.g., |d1−d2|≤100 nm.
In some embodiments, the via 820 may optionally contain, in the bottom portion thereof, a distributed Bragg reflector (DBR) mirror 810, with the layer stack 822/824/826 being vertically above the DBR mirror in the via. As known in the pertinent art, a DBR mirror can be formed, e.g., using a stack of semiconductor and/or dielectric layers, each having a quarter-wavelength thickness, with adjacent layers of the stack having alternating refractive indices. For example, DBR mirror 810 may be formed using a suitable number of silicon and silicon oxide layers. In operation, DBR mirror 810 may reflect a portion of the modulated optical signal 308 that has not been absorbed on the first pass through the layer stack 822/824/826. At least some of the reflected light can thus be absorbed in the layer stack 822/824/826 on the second pass therethrough, which can beneficially increase the effective light sensitivity of photodiode 710.
In an example embodiment, chipset 900 comprises a fiber assembly block (FAB) 910, a vertical chip stack 930, and an array of male or female socket connectors 950.
FAB 910 includes end segments of a plurality of optical fibers 920, different ones of which may implement individual ones of optical fibers 192, 194, or 286. End segments of optical fibers 920 are sandwiched between two glass plates (not explicitly shown in
Chip stack 930 comprises PIC 170 and integrated circuit 130, which are attached to one another such that main surface 402 of the PIC is at the top surface of the chip stack. FAB 910 can be attached to surface 402 of chip stack 930, e.g., as indicated above.
In some embodiments, chip stack 930 can be replaced by a single chip designed and configured to implement the functions of both PIC 170 and integrated circuit 130.
In the shown example embodiment, socket connector 950 comprises a plurality of electrical pins 952 at the bottom surface thereof. Socket connector 950 further comprises a plurality of contact pads 948 at the top surface thereof. The body of socket connector 950 includes a metal interconnect (not explicitly shown in
In the embodiment shown in
The distances between the V-shaped grooves of glass plate 1006 are selected such that the different optical fibers 920 of FAB 910 can be appropriately optically aligned with the corresponding circuit elements of PIC 170 when end surface 916 is glued to main surface 402 of PIC 170. For example, some of the optical fibers 920 can be optically aligned with gratings 510 of different respective vertical-coupling elements 410. Some other optical fibers 920 can be optically aligned with photodiodes 710 of different respective photodetectors 310. In general, the V-shaped grooves of glass plate 1006 are arranged such as to match the arrangement of the vertical-coupling elements 410 and photodetectors 310 on the main surface 402 of PIC 170 (also see
In some embodiments, each optical fiber 920 may end-connect to the near end of a corresponding co-linear optical mode converter, and opposite ends of said optical mode converters may be equidistant with the end surface 916 to provide an array of low-loss optical couplers to vertical-coupling elements 410 and photodetectors 310 on the main surface 402 of PIC 170.
In an example embodiment, the above-mentioned different distances d1 and d2 or the same distance d (
In various embodiments, different optical fibers 920 may be of the same type or of different types. As an example,
According to an example embodiment disclosed above, e.g., in the summary section and/or in reference to any one or any combination of some or all of
In some embodiments of the above apparatus, the apparatus further comprises a fiber assembly block (e.g., 910,
In some embodiments of any of the above apparatus, end segments of the optical fibers in the fiber assembly block are oriented with respect to said end surface at an angle (e.g., α,
In some embodiments of any of the above apparatus, the fiber assembly block has end segments of at least 50 optical fibers.
In some embodiments of any of the above apparatus, the plurality of in-line optical modulators is further waveguide-connected in the substrate to at least one second vertical-coupling element (e.g., 4100,
In some embodiments of any of the above apparatus, the apparatus further comprises one or more optical splitters (e.g., 4201-4207,
In some embodiments of any of the above apparatus, the apparatus further comprises a fiber assembly block (e.g., 910,
In some embodiments of any of the above apparatus, the fiber assembly block has end segments of at least 100 optical fibers.
In some embodiments of any of the above apparatus, the photodiodes and the first vertical-coupling elements are arranged in a linear array along said main surface.
In some embodiments of any of the above apparatus, top semiconductor surfaces of the photodiodes and top semiconductor surfaces of the first vertical-coupling elements are located at approximately same vertical distance (e.g., d,
In some embodiments of any of the above apparatus, top semiconductor surfaces of the photodiodes and top semiconductor surfaces of waveguide cores of the in-line optical modulators are located at approximately same vertical distance (e.g., d,
In some embodiments of any of the above apparatus, at least one of the in-line optical modulators comprises a Mach-Zehnder modulator (e.g., 440,
In some embodiments of any of the above apparatus, each of the in-line optical modulators comprises a sequence of end-connected Mach-Zehnder modulators (e.g., 440,
In some embodiments of any of the above apparatus, the apparatus further comprises a plurality of optical data receivers (e.g., 1841-184M,
In some embodiments of any of the above apparatus, the photodiodes are buried in respective vias (e.g., 820,
In some embodiments of any of the above apparatus, the substrate comprises a base layer (e.g., 802,
In some embodiments of any of the above apparatus, at least some of the vias penetrate the insulator layer and enter the base layer (e.g., as shown in
In some embodiments of any of the above apparatus, the base layer comprises silicon; the insulator layer comprises silicon oxide; the device layer comprises silicon; and the photodiodes comprise germanium.
In some embodiments of any of the above apparatus, at least some of the vias have Bragg reflectors (e.g., 810,
In some embodiments of any of the above apparatus, the plurality of in-line optical modulators is further waveguide-connected in the substrate to at least one second vertical-coupling element (e.g., 4100,
In some embodiments of any of the above apparatus, the in-line optical modulators are configured to modulate the carrier light to generate the output light.
In some embodiments of any of the above apparatus, the apparatus further comprises one or more optical splitters (e.g., 4201-4207,
In some embodiments of any of the above apparatus, the apparatus further comprises a fiber assembly block (e.g., 910,
In some embodiments of any of the above apparatus, each of the first vertical-coupling elements comprises a respective optical grating (e.g., 510,
While this disclosure includes references to illustrative embodiments, this specification is not intended to be construed in a limiting sense. Various modifications of the described embodiments, as well as other embodiments within the scope of the disclosure, which are apparent to persons skilled in the art to which the disclosure pertains are deemed to lie within the principle and scope of the disclosure, e.g., as expressed in the following claims.
Unless explicitly stated otherwise, each numerical value and range should be interpreted as being approximate as if the word “about” or “approximately” preceded the value or range.
It will be further understood that various changes in the details, materials, and arrangements of the parts which have been described and illustrated in order to explain the nature of this disclosure may be made by those skilled in the art without departing from the scope of the disclosure, e.g., as expressed in the following claims.
The use of figure numbers and/or figure reference labels in the claims is intended to identify one or more possible embodiments of the claimed subject matter in order to facilitate the interpretation of the claims. Such use is not to be construed as necessarily limiting the scope of those claims to the embodiments shown in the corresponding figures.
Although the elements in the following method claims, if any, are recited in a particular sequence with corresponding labeling, unless the claim recitations otherwise imply a particular sequence for implementing some or all of those elements, those elements are not necessarily intended to be limited to being implemented in that particular sequence.
Reference herein to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the disclosure. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments necessarily mutually exclusive of other embodiments. The same applies to the term “implementation.”
Unless otherwise specified herein, the use of the ordinal adjectives “first,” “second,” “third,” etc., to refer to an object of a plurality of like objects merely indicates that different instances of such like objects are being referred to, and is not intended to imply that the like objects so referred-to have to be in a corresponding order or sequence, either temporally, spatially, in ranking, or in any other manner.
Throughout the detailed description, the drawings, which are not to scale, are illustrative only and are used in order to explain, rather than limit the disclosure. The use of terms such as height, length, width, top, bottom, is strictly to facilitate the description of the embodiments and is not intended to limit the embodiments to a specific orientation. For example, height does not imply only a vertical rise limitation, but is used to identify one of the three dimensions of a three dimensional structure as shown in the figures. Such “height” would be vertical where the electrodes are horizontal but would be horizontal where the electrodes are vertical, and so on. Similarly, while some of the figures show the different layers as horizontal layers such orientation is for descriptive purpose only and not to be construed as a limitation.
Also for purposes of this description, the terms “couple,” “coupling,” “coupled,” “connect,” “connecting,” or “connected” refer to any manner known in the art or later developed in which energy is allowed to be transferred between two or more elements, and the interposition of one or more additional elements is contemplated, although not required. Conversely, the terms “directly coupled,” “directly connected,” etc., imply the absence of such additional elements. The same type of distinction applies to the use of terms “attached” and “directly attached,” as applied to a description of a physical structure. For example, a relatively thin layer of adhesive or other suitable binder can be used to implement such “direct attachment” of the two corresponding components in such physical structure.
The description and drawings merely illustrate the principles of the disclosure. It will thus be appreciated that those of ordinary skill in the art will be able to devise various arrangements that, although not explicitly described or shown herein, embody the principles of the disclosure and are included within its spirit and scope. Furthermore, all examples recited herein are principally intended expressly to be only for pedagogical purposes to aid the reader in understanding the principles of the disclosure and the concepts contributed by the inventor(s) to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions. Moreover, all statements herein reciting principles, aspects, and embodiments of the disclosure, as well as specific examples thereof, are intended to encompass equivalents thereof.
Patent | Priority | Assignee | Title |
Patent | Priority | Assignee | Title |
10025043, | Mar 15 2016 | Senko Advanced Components, Inc | Optical alignment of an optical subassembly to an optoelectronic device using pairs of alignment reflective surfaces |
10345522, | Sep 20 2017 | Lumentum Operations LLC | Multi-core silicon waveguide in a mode-converting silicon photonic edge coupler |
6181864, | Aug 14 1997 | Samsung Electronics Co., Ltd.; SAMSUNG ELECTRONICS CO , LTD | Optical fiber array module using soldering and fabrication method thereof |
6377732, | Jan 22 1999 | TYCO ELECTRONICS SERVICES GmbH | Planar waveguide devices and fiber attachment |
7542636, | Sep 25 2002 | HOYA Corporation USA | Optical assemblies for free-space optical propagation between waveguide(s) and/or fiber(s) |
8483528, | Feb 29 2008 | GOOGLE LLC | Optical mode transformer, in particular for coupling an optical fiber and a high-index contrast waveguide |
8750654, | Dec 17 2009 | WSOU Investments, LLC | Photonic integrated circuit having a waveguide-grating coupler |
9927575, | Jun 25 2015 | HUAWEI TECHNOLOGIES CO , LTD | Optical coupling using polarization beam displacer |
20040037519, | |||
20050013558, | |||
20050053319, | |||
20070132064, | |||
20070237444, | |||
20080240645, | |||
20140270784, | |||
20150037044, | |||
20150125110, | |||
20150293305, | |||
20170123170, | |||
20170168235, | |||
20170227723, | |||
20180196196, | |||
20180329159, | |||
20190107673, | |||
20190243164, | |||
20190258175, | |||
20200409001, | |||
20210333472, |
Executed on | Assignor | Assignee | Conveyance | Frame | Reel | Doc |
Feb 28 2020 | DOS SANTOS FEGADOLLI, WILLIAM | NOKIA SOLUTIONS AND NETWORKS OY | ASSIGNMENT OF ASSIGNORS INTEREST SEE DOCUMENT FOR DETAILS | 052467 | /0641 | |
Apr 22 2020 | NOKIA SOLUTIONS AND NETWORKS OY | (assignment on the face of the patent) | / |
Date | Maintenance Fee Events |
Apr 22 2020 | BIG: Entity status set to Undiscounted (note the period is included in the code). |
Date | Maintenance Schedule |
Nov 22 2025 | 4 years fee payment window open |
May 22 2026 | 6 months grace period start (w surcharge) |
Nov 22 2026 | patent expiry (for year 4) |
Nov 22 2028 | 2 years to revive unintentionally abandoned end. (for year 4) |
Nov 22 2029 | 8 years fee payment window open |
May 22 2030 | 6 months grace period start (w surcharge) |
Nov 22 2030 | patent expiry (for year 8) |
Nov 22 2032 | 2 years to revive unintentionally abandoned end. (for year 8) |
Nov 22 2033 | 12 years fee payment window open |
May 22 2034 | 6 months grace period start (w surcharge) |
Nov 22 2034 | patent expiry (for year 12) |
Nov 22 2036 | 2 years to revive unintentionally abandoned end. (for year 12) |